Journal of Computer and Knowledge Engineering
Volume:6 Issue: 2, Summer-Autumn 2023

In different scientific disciplines, large-scale data are generated with enormous storage requirements. Therefore, effective data management is a critical issue in distributed systems such as the cloud. As tasks can access a nearby site to access the required file, replicating the desired file to an appropriate location improves access time and reliability. Replicating the popular file to an appropriate site is a good choice, as tasks can get the necessary file from a nearby site. In this research, a novel data replication algorithm is proposed that is consisted of four main phases: 1- determining 20% of commonly used files, 2- computing five conflicting objectives (i.e., average service time, load variance, energy consumption, average response time and cost) 3- finding the near-optimal solution (i.e., suitable locations for new replica) by the PSO technique to acquire a trade-off among the desired objectives. 4- replica replacement considering a fuzzy system with three inputs (i.e., Number of accesses, size of replica and the last access time). The experimental results denote that the proposed replication algorithm outperforms the Profit oriented Data Replication (PDR) and Bee colony-based approach for Data Replication (BCDR) strategies in terms of energy consumption, average response time, load variance, number of connections, Hit ratio, Storage usage, and cost.

Secret sharing schemes are ideally suited to save highly sensitive information in distributed systems. On the other hand, Zigzag-Decodable (ZD) codes are employed in wireless distributed platforms for encoding data using only bit-wise shift and XOR operations. Recently, Vandermonde-based ZD codes have been utilized in secret sharing schemes to achieve high computational efficiency such that sharing and recovering of secrets can be realized by lightweight operations. However, the storage overhead of using these ZD codes remains a problem which is addressed in the present paper. Here, a ramp secret sharing scheme is proposed based on an efficient ZD code with less storage overhead in comparison with existing literature. The novelty of the proposed scheme lies in the careful selection of the number of positions to shift the bits of the secret such that security and zigzag decodability are guaranteed simultaneously. In addition to prove gaining these features, we show that the scheme improves speed of recovery.

In wireless communication channels, the channel coefficients are dependent on each other. This paper investigates the constructive or destructive effects of fading coefficients correlation of wireless multiple access channels (MAC) on the outage probability (OP) (one of the wireless communications performances). The desired channel in this paper is a wireless Rayleigh fading MAC with three-users, independent sources, and interdependent fading coefficients; The Copula theory is used as the tool to model the dependence structure. A closed-form expression for the channel outage probability is obtained using an important family of Copulas named the Farlie-Gumbel-Morgenstern (FGM) Copula. The results show that the negative dependence structure of the channel coefficients has a constructive effect on the outage probability; in other words, it reduces the outage probability values compared to the independent case. in contrast, the positive dependency has a destructive effect on the outage probability. The efficiency of the analytical results is illustrated numerically, and the numerical illustrations confirm the theoretical results.

 Maximizing WSN longevity besides maintaining their efficiency and proper performance, is one of the most important challenges that researchers of this field encounter. FlexiTP, is a protocols that was designed and made for optimizing energy consumption and maximizing longevity of these kinds of networks. This study presents improved version of FlexiTP protocol using Harmony Search algorithm with the objective of optimizing energy consumption of FlexiTP protocol. The suggested method, HS-FlexiTP, is able to choose the best parent for each sensor node, using Harmony Search algorithm, based on three criterion including; distance of parent node from child node, number of the hops of the parent node and remaining energy of the parent node. Obtained results of the simulations indicate that HS-FlexiTP is able to decrease 25 percent of the consumed energy per each node throughout the various scenarios of simulation in comparison with FlexiTP protocol. In comparison with ZMAC protocol, it has much better efficiency in decreasing consumed energy as well and in comparison with both protocols, ZMAC and FlexiTP, the suggested procedure is able to maximize network longevity and optimize other efficiency criteria including average packet delay, throughput and productivity of the channel.

Today’s cyber-attacks are getting more sophisticated and their volume is consistently growing. Organizations suffer from various attacks in their lifetime each of which exploiting different vulnerabilities, therefore, preventing them all is not affordable nor effective. Hence, selecting the optimal set of security countermeasures to protect IT assets from being compromised is a challenging task which requires various considerations such as vulnerabilities characteristics, countermeasures effectiveness, existing security policies and budget limitations. In this paper, a dynamic security risk management framework is presented which identifies the optimal risk mitigation plans for preventing ongoing cyber-attacks regarding limited budget. Structural and probabilistic analysis of system model are conducted in two parallel and independent aspects in which the most probable system's risk hotspots are identified. Suitability of countermeasures are also calculated based on their ability in covering vulnerabilities and organizational security policies. Moreover, a novel algorithm for dynamically conducting cost-benefit analysis is proposed which identifies optimal security risk mitigation plans. Finally, practical applicability is ensured by using a case study.

With the emergence of IoT devices, data aggregation in the area of smart grids can be implemented based on IoT networks. However, the communication and computation resources of IoT devices are limited so it is not possible to apply conventional Internet protocols directly. On the other hand, gathering data of smart meters in the advanced metering infrastructure faces challenges such as privacy-preserving and heavy-loaded authentication and aggregation schemes. In this paper, we propose an improved lightweight, secure, and privacy-preserving scheme for aggregating data from smart meters in large-scale IoT-based smart grids. The proposed scheme adopts light-weight cryptography operations such as exclusive-OR, hash, and concatenation functions. In comparison with the schemes in the literature, the analysis and simulation results show that the proposed scheme satisfies the same security levels, while at the same time burdens lower computation and communication overheads. This observation makes the proposed scheme more suitable to be employed in large-scale and IoT-based smart grids for data aggregation.